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Flashcard > Biology Topic 6 > Flashcards

Biology Topic 6 Flashcards

1
Q

What is meiosis?

A

The formation of four non-identical cells from a singular cell.

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2
Q

What is mitosis?

A

The formation of two identical cells from a singular cells.

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3
Q

What is sexual reproduction?

A

It involves the joining of male and female gametes, each containing genetic information.

Animals : sperm and egg cells.
Flowering plants: Pollen and egg cells.

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4
Q

What process forms gametes?

A

Meiosis, as they are not identical.

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5
Q

How many chromosomes do gametes have?

A

23

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6
Q

How is variation produced in an offspring?

A

The genetic info from each parent is mixed, producing variation in the offspring.

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7
Q

What is asexual reproduction?

A

Reproduction, which involves one parents, with the absence of gametes fusing.

It happens using the process of mitosis, where 2 identical cells are produced from a singular cell.

There is no mixing of genetic information.

This process leads to clones, which are genetically identical to each other and the parent.

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8
Q

What organisms asexually reproduce?

A

Bacteria, some plants and even some plants.

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9
Q

Explain the process of meiosis?

A
  1. DNA duplicates. Each chromosome has a copy of itself.

2.The chromosomes line up at the equator in pairs. One from the mother and one from the father.

  1. The cell undergoes the first division in meiosis 1. The pairs of chromosomes are pulled apart. Some of the mother’s chromosomes and some of the father’s chromosomes go into the new cells, creating a mixture of their chromosome. This mixes up the genes and creates genetic variation in the offspring.
  2. The chromosomes line up at the equator again in both cells.
  3. The 2 cells undergo the second division in meiosis 2. The arms of the chromosomes (chromatids) are pulled apart.
  4. The gametes are made as 4 haploid daughter cells. Each of the gametes is genetically unique from one another and they only have a single set of chromosomes (23 chromosomes). Hence, they are haploid.
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10
Q

Explain the process of mitosis?

A
  1. Interphase - The cell spends most of its life in this phase. The DNA in chromosomes copies itself ready for mitosis.
  2. Prophase - The DNA in chromosomes and their copies condenses to become more visible. The membrane around the nucleus disappears.
  3. Metaphase - Chromosomes and their copies line up in the middle of the cell.
  4. Anaphase - Chromosomes and their copies are pulled to different ends of the cell.
  5. Telophase - New membranes form around the chromosomes at each end of the cell.
  6. Cytokinesis - The cell membrane pinches in and eventually divides into two daughter cells.
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11
Q

Advantages of sexual reproduction:

A
  1. Produces variation in offspring
  2. It allows us to use selective breeding.
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12
Q

Why is variation in offspring an advantage?

A
  1. This means that if the environment changes, it is likely that an organism in the species will have a characteristic that allows them to survive. ( Survival Advantage.)
  2. Although some individuals may die, variation decreases the chance of the whole species becoming extinct.
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13
Q

Why is us being able to use selective breeding an advantage of sexual reproduction?

A
  1. This type of reproduction mixes the genetic information from 2 organisms
  2. Organisms with different desirable characteristics can be bred to produce offspring with even more desirable characteristics.

An example of this could be to increase food production, we could breed two animals with lots of meat.

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14
Q

Advantages of asexual reproduction:

A
  1. Only one parent is required.
  2. Uses less energy and is faster, as the organism does not need to find a mate.
  3. In favourable conditions, lots of identical offspring
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15
Q

Examples of organisms that use both methods to reproduce:

A
  1. Strawberries
  2. Daffodils
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16
Q

What is the chemical that makes up the genetic material in the nucleus?

A

DNA ( deoxyribonucleic acid)

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17
Q

What is DNA ( in terms of structure)?

A

A polymer, made up of two strands in the form of a double helix.

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18
Q

What is DNA in the nucleus contained in?

A

chromosomes

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19
Q

What is a gene?

A

A small section of DNA on a chromosome
A triplet of bases, that code for a specific protein.

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20
Q

What is a genome?

A

All the genes coding for all the proteins within an organism.

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21
Q

What is DNA made of?

A

Small parts called nucleotides

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22
Q

What are nucleotides made up of?

A
  1. Pentose sugar
  2. Phosphate
  3. One of the four types of organic bases
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23
Q

What are the 4 kinds of organic bases?

A

A,T,G,C

24
Q

What are the complementary base pairing?

A

A - T
G - C

25
Q

How many bases code for an amino acid?

A

3

26
Q

What determines what sort of protein is made?

A

The types and order of amino acids

27
Q

How many types of amino acids are there?

A

20

28
Q

What do the non-coding part of the DNA do?

A

Some are responsible for switching genes on and off.

29
Q

Describe the process of protein synthesis

A
  1. DNA contains the genetic code, for making a protein, but it cannot move out of the nucleus, because it is too big.
  2. The double helix structure pulls apart into its 2 strands. mRNA nucleotides match to their complimentary base on the strand.
  3. The mRNA nucleotides join together, to form a template of the original DNA.
  4. The mRNA is able to move out the nucleus, and does so. It goes to the cytoplasm, and onto the ribosomes.
  5. At the ribosome, the bases on the mRNA are read in triplets, to code for an amino acid.
  6. The corresponding amino acids are bought to the ribosomes by carrier molecules.
  7. These amino acids connect together to form a protein.
  8. When the chain is complete, the protein folds to form a unique 3D structure,
30
Q

3 possible things proteins can be

A
  1. Hormones
  2. Enzymes
  3. Structural protein.
31
Q

What does a mutation do?

A

It changes the sequences of bases in DNA.

32
Q

What are the 3 things a mutation could possibly do, in terms of bases?

A
  1. A base is inserted into the code.
  2. A base is deleted from the code.
  3. A base is substituted.
33
Q

What is the problem with a mutation occurring for proteins?

A
  1. Shape of protein changes.
  2. The substrate will not fit into the active site and they are no longer complementary and so cannot bind.
34
Q

What is an allele?

A

An allele is a different form of the gene.
Humans have two alleles for each gene as they inherit one from each parent

35
Q

What is a dominant allele?

A

Only one is needed for the the characteristic to be expressed and for the phenotype to be observed

36
Q

What is the recessive allele?

A

two copies are needed for it to be expressed in for the corresponding that phenotype should be observed

37
Q

What is homozygous?

A

When both inherited alleles are the same

38
Q

What is heterozygous?

A

When one of the alleles are dominant and the other is recessive

39
Q

What is the Genotype?

A

The combination of alleles an individual has. For example Aa

40
Q

What is phenotype?

A

The physical characteristics are observed in the individual. For example eye colour

41
Q

2 most commonly inherited genetic disorders:

A
  1. Cystic fibrosis
  2. Polydactyly
42
Q

What is polydactyly?

A

Having extra fingers or toes
due to a dominant allele

43
Q

Where is cystic fibrosis?

A

A disorder of the cell membranes resulting in thick mucus in the Airways and pancreas

Caused by a recessive allele.

44
Q

What is embryonic screening?

A

This allows scientists to observe whether the child will have a genetic condition or not

45
Q

What occurs in embryonic screening?

A
  1. If the embryos developed in the lab, cells can be taken from it and analyses
  2. or DNA from the embryo in the womb can also be extracted
46
Q

What are the arguments for embryonic screening?

A
  1. Reduces the number of people suffering so this is ethically correct
  2. Treating disorders is very expensive so this is economically considerate
    three. There are many regulations in place to stop it getting out of control so this is socially maintained.
47
Q

Arguments against embryonic screening?

A
  1. This could lead to the idea of designer babies, where it could encourage people to pick characteristics and this is ethically wrong
  2. It is expensive to carry out the screening so this is economically difficult
  3. May promote prejudice as it suggests that those with genetic disorders care will not live a full life or unwanted so this is socially wrong.
  4. This can be emotionally challenging because terminating a pregnancy would have to be made
  5. The procedure can lead to a miscarriage
48
Q

What does the 23rd pair of chromosomes carry?

A

Sex determining genes

49
Q

What is XY?

A

male

50
Q

What is XX?

A

Female

51
Q

What are the two factors that impact the phenotype of an organism?

A
  1. Genotype
  2. Environment
52
Q

How is genotype a factor of phenotypes?

A

Genes are passed on from the parent in sex cells.
The combining of genes from the mother and father creates genetic variation.

53
Q

How is environment a factor of phenotypes?

A

The conditions the organism grows and develops in, can also affect its appearance.

54
Q

What is evolution?

A

A change in the inherited characteristics of a population over time.
Through a process of natural selection, which may result in the formation of a new species.

55
Q
A

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